This invention relates to self-assisting plasma rings. For purposes of this application, a self-assisting plasma ring is defined as an inductively formed, compact toroid containing a self-assisting, current carrying plasma. The current circulates around an annulus with a central X axis and Y and Z axes at right angles to each other and the X axis in a cartesian coordinate system.
Unlike the structure of a smoke ring, the self-assisting plasma rings of this invention, which are referred to hereinafter as "plasma rings" for ease of explanation, are substantially rigid due to the internal circulating electrical currents. To this end, the plasma ring contains internal, self-assisting currents I.sub.p that circulate in the plasma to sustain the ring along an endless axis in the ring mid-plane, which is normal to the X axis. Still further, the inductive formation of the plasma ring requires that it have externally produced equilibrium fields (EF).
Plasma rings have been known in the electrical arts in general, and the field of physics in particular since about the time that ball lighting, which contains self-assisting plasma currents, was first recognized as having distinctly rigid characteristics. U.S. patent application Ser. No. 283,823 filed Mar. 28, 1972, now abandoned, which is incorporated by reference herein, describes a plasma ring with self-assisting currents. Also, 46 Phys. Rev. Letters 188-91 describes the actual formation and use of plasma rings for transforming a gas into a substantially rigid, current carrying plasma ring in a spheromak.
Such substantially rigid, current carrying plasma rings can be inductively formed in a vacuum chamber in a spheromak. To this end, in one method, the plasma is formed around a toroidal flux core in the vacuum chamber. Then, the plasma contracts into a compact toroid that is held in equilibrium by the externally produced equilibrium fields (EF). However, the currents circulating in the plasma ring produce magnetic fields that interact with the equilibrium field, which may be steadystate, to produce unstable tilting and/or shifting modes. Such unstable tilting and/or shifting modes, are described in the "PS-1 Spheromak Experiment," by H. Bruhns, et al., and "Tilting-Mode-Stable Spheromak Configuration," by K. Yamazaki, in Los Alamos Scientific Laboratory Report LA-8700-C, pp 93-100, which are incorporated by reference herein.
One system for counteracting, eliminating or impeding one or more of these instabilities is to shape the outside of the plasma. To this end, for example, the plasma can be adiabatically compressed. One compression method is described for example, in U.S. Pat. No. 3,702,163. Another technique is to use active, multipole-field conductors on the inside of the vacuum chamber. However, these systems require, active conductors, power supplies, and complicated and expensive feed-back controls.
These and other unique problems associated with plasma rings require that the desired stabilizing means be simple and inexpensive to build and operate. Also, the stabilizing means should not interfere unduly with the operation of the plasma rings or the access thereto, since an important advantage of plasma rings is that they provide the maximum self-assistance and freedom from external constraints. It is also advantageous that passive conductors be employed.
It is, accordingly, a general object of this invention to provide simple and inexpensive passive conducting means for stabilizing plasma rings having unstable tilting and/or shifting modes.
Another object of the invention is to provide passive conducting loops for stabilizing the tilting and/or shifting modes of plasma rings in a spheromak.
A still further object is to provide a passive method for stabilizing a plasma ring having externally produced equilibrium fields and internal plasma currents that interact to tilt and/or to shift the plasma ring.
The above and further novel features and objects of this invention will appear more fully from the following detailed description of one embodiment of this invention when the same is read in connection with the accompanying drawings, and the novel features will be particularly pointed out in the appended claims. It is to be expressly understood, however, that the drawings are not intended as a definition of the invention but are for purposes of illustration only.